Road surfacing composition and method of making same



Patented Feb. 16, 1932 7 sAM E. FINLEY, or

7 ROAD SURFAGING COMPOSITION N Drawing; 7 Application filed December My invention relates to a novel road surfacing compositionand the method of making same, and has to do, moreparticularly, with the production of a paving material of the bituminous cement type which can be laid cold and set to form a tough,malleable, durable, wear-resistant and water-proof pavement'by the application of pressure thereto at ordinary atmospheric temperatures. This 10 application is a continuation in part of my pending application for improvements in road surfacing composition and method of making same, Serial No. 425746, filed January 30, 1930.

lhe main object of my invention is to provide a road surfacing composition of the bi tuminous cement type, which is readily workable, and adapted to storage and transportation, retaining its mobility and workability during such storage and transportation, and which can be laid cold andset, by the application of pressure at ordinary atmospheric temperatures, to form a tough, malleable, durable, wear-resistant and waterproof pavement. A

A further object of my invention is to provide a new road surfacing composition and method of making the same of such charac ter that the softnessor penetration ofthe binder serving as a bond between the particles of aggregate, in a road surface constructed from such composition, may be effectively controlled and varied by'properly selecting the materials used to make the composition,

with especial regard to the penetration or viscosity of such materials.

Another object of my invention is to provide a novel road surfacing composition,

which can be spread and set to form a pave- :40 ment in either thick or thin layers, that is to say, of such a character that it doesnot need to be applied to the roadway in layers of fixed thickness, in order that the workability of the composition may be retained. Another obi ject is to provide a road surfacing composi tion such that it may be readily workedand spread in thin layers having a high percentage of bituminous material to form the road surface, without impairing the workability of the composition, as distinguished from hot ATLANTA, GEORGIA AND METHOD or MAKING SAME 2, 1931, Serial No. 578,616.

mixes, which cannot be employed in thin layers on the road surface with more than 10% or.11% of bitumen, due to the difficulty. of raking, levelling and distributing the mixture. A further object of my invention is to provide a road surfacing composition of the bituminous cement type of such character that, when laid on a road bed and set by pressure to form a pavement, there willbe provided a reserve supply of cementitious material for future use, to serve as an additional bond when tratlic has ultimately worn down the aggregate sufficiently to call it into service and thus prevent the formation of cracks. Another object is to provide a road surfacing composition ofsuch character as to provide a priming coat to act as an added bond between the foundation and the, paved surface.

A further object of my invention is topro vide a road-surfacing composition, which, when caused to set, will provide a roughened, non-skid traction surface, but one which is thoroughly water-proof so that water cannot penetrate the pavement to efiect deterioration therein.

A further object of my invention isto provide a novel road surfacing composition from which better road structures may be built, and of such a nature that the construction of roads therefrom is more efficient and less costly, due to economies in labor, equipment and materials resulting from its use.

Further objects, and objects relating to details and economies of use and operation, 35 will definitely appear from the detailed description to follow. In one instance, I accomplish the objects of my invention by the means described in the following specification. .My invention is clearly defined and pointed outin the appended claims.v V

r In general, my invention consists in coating the aggregate with a relatively heavy bituminous cement, which, in turn, is provided with a supercoating of a relatively light bitumen having the qualities of a flux, either of which may be derived from petroleum, asphalt or coal tar. The road surfacing composition of my'invent'ion consists of a min eral aggregate the individual particles of storage, transportation and application to -dia.

which have an inner coating of stable bituminous cement and an outer coating of a bituminous flux, devoid of light volatile matter, and fluid at ordinary atmospheric temperatures, which flux must be of such a character as to be capable of amalgamation with the inner coating to form a bituminous cement of higher penetration than said inner coating. My method of making such road-surfacing composition consists in applying a coating of stable bituminous cement to the individual particles of a mineral aggregate and, then, directly applying to such coated particles a supercoating of bituminous flux of the character above stated. Under certain conditions, it may be found advantageous to apply the coatings in the form of any of the well known emulsions of the bituminous me The mobility and workability of the road-surfacing composition, in the cold,

'arises from the circumstance that, when the elements or particles of the aggregate so coated come into contact, actual contact is between the fluid films of light bitumen constituting the super-coatings, hence the particles are readily movable in the mass and the latter is easily shoveled, raked screeded or luted into place as road surfacing material.

While the mobility and workability of the composition are of prime importance in the surfacing streets, roadways and the like, the mode of applying the binder and the flux to the aggregate admits of the selection of a medium for the initial coat of such consistency in terms of penetration or specific viscosity that, when ultimately merged or amalgamated with the bituminous super-coat, which latter is of selectively determined consistency, the'mixture will be of the desired predetermined consistency to produce, the best effects in binding or cementing together the elements of the aggregate and produce the desired surface coating, when set by the application of pressure, that is wearresisting water-proof, tough and malleable and, therefore, of a character best adapted to withstand the varying conditions of traffic and weather,

- without impairment.

The combining of heavy and light bitumen in two films has been termed amalgama- "tion. This amal amation ma be hastened or retarded by controllable factors, as follows: Vhen stored in bulk and protected in piles from air currents, from the suns heat and from pressure, the amalgamation proceeds very slowly. This enables me to store such mixtures for considerable periods with terial is taken from the storage piles and spread in thin layers upon the street, it immediately becomes exposed to air currents,

to the suns heat, and to the'pressure of the higher penetration than such coating. I

make use of this phenomenon by forming a road-surfacing composition in which the individual particles of the aggregate have an inner coating of stable bituminous cement and a fluid outer coating of bituminous flux.

So long as the fluid outer coating remains;

the mass retains its mobility and workability, because this fluid super-coating enables the particles of the mass to move readily relative to each other, but the application of pressure to the mass after it has been worked and spread into position in the road-bed, effects an amalgamation of the-fluid super-coating with the inner coating of bituminous cement, forming by the amalgamation of these two coatings a bituminous cement of higher penetration than the inner coating which acts as the binder, cementing the individual particles of the aggregate together to form a wearresisting and water-proof road surface.

lVhile the fluid super-coating is important as imparting mobility and workability to the mass prior to the application of pressure, it is also important that nothing should be interposed between the inner coating of stable bituminous cement and this super-coating to interfere with the amalgamation of the two coatings which is brought about after the -material has been spread upon the roadway by the application of pressure thereto. I do not introduce into the mixture any filler or separator of a non-cementitious nature to promote the mobility and workability of the material and my invention does not contemplate the use of filling or separating material, such, for instance, as limestone dust, the use of which is proposed in the Nicholson Patent, No. 1,778,461, as a means for imparting mobility and workability to a road-surfacing composition. Whenever, in this specification and the appended claims, I refer to the super coating of bituminous flux as directly applied to the inner coating of bituminous cement, I have in mind the fact that no filler or separator such as this limestone dust is to be used and means that there is nothing interposed between the inner coating of bituminous cement and the super-coating of bituminous flux to interfere with the amalgamation of these two coatings under pressure.

The medium for the initial coat, depending upon the product to be produced and the wear-resistance to traffic required in the road to be made therefrom, may be a bituminous cement of from 10 to 7 penetration at 77 F., and the flux coat may consist'of bitumen re fined to a consistency of from 40% of 100 penetration to 80% of 100 penetration at 7 7 F., depending upon the desired consistency of the ultimate binding medium after amalgamation. This bituminous cement of the inner coating will be solid at ordinary atmospheric temperatures, while the flux will be fluid at such temperatures. When coal tar products are employed for the respective coatings of the aggregate, the first coating should be a relatively heavy coal tar cement having a melting point of from 125 F. to 17 F., and the super-coating of flux may be a coal tar product also freed from quick volatiles and having a specific viscosity (Engler) between and at C. Obviously, these cementitious and fluxing derivatives of coal tar which are bituminous media may also be applied in the form of emulsions.

The application of the bituminous coatings to the mineral aggregate in the form of emulsions is of advantage in some instances and in certain grades of aggregate, in that it admits of the heavy and light bituminous menstrua of the desired consistency being selected, so that, after applicationof the respective coatings and when the emulsion is broken, the media will be left in the original condition before emulsification or combination thereof.

In carrying out my invention, the aggregate in the form of broken stone, gravel, slag, sand or the like, is heated in suitable apparatus for the purpose of surface drying or removing the moisture therefrom, and is then placed in any suitable mixing apparatus. The aggregate is relatively cold as compared with similar aggregate employed in the standard practice of manufacturing bituminous cement aggregate mixtures of high stability, that is to say,t'he residual temperature resulting from .the drying operation will not be suflicient to prevent the stable bituminous cement adhering to the surface of the aggregate, and, ordinarily, the temperature of the aggregate at this stage of the process will vary from 120 F. to 200 F. To the mineral aggregate in the mixing apparatus there is added a heavy, refined, bituminous cement, such, for example, as one having a penetration of 10 to at 77 F., which has been heated to approximately 400 F., as a preliminary or inner coating to the in dividual particles of the aggregate in the desired percentage and which, because of the materially lower temperature of the aggregate, will form a relatively heavy coating, as compared with the thin coating which would result if the aggregate were added to the degree required in ordinary practice. When the aggregate has been substantially and uniformly coated with a heavy bitumen, there 1s added a super-coating in the form of a bituminous flux, which may be refined bituminous residuum resulting from the heat treatment of'crude'bitumen at temperatures from 250 F. upward, which causes the latter to give up its light volatiles, such as naphtha, gasoline, kerosene, or the like, the said residuum being fluid at ordinary atmospheric temperatures, of a consistency of from 40% to 80% bitumen of 100 penetration at 77 F., and, as stated, devoidof the light or quick volatiles. The aggregate which has been subjected to the two coatings of bitumen, one a relatively hard, highly stable bitumen, and the other a supercoating of bitumen, refined to a consistency within the limits of the percent specified of 100 penetration and devoid of light volatiles, may be stored for subsequent use, or transported for relatively long distances.

7 No material amount of amalgamation will take place between the inner coating and the super-coating without the application of pres sure and, therefore, the fluid super-coating of bituminous flux remains upon the individual particles of the aggregate until pressure is applied thereto, and the material retains its mobility and workability prior'to the application of pressure, with the result that the material may be stored for considerable periods of time, transported for considerable distances, and there distributed, spread and leveled into position upon the road-bed at ordinary atmospheric temperatures. When the material has been spread and leveled in position to form the road surface, pressure may be applied thereto, as by running a road roller thereover, which causes an amalgamation of the inner coating and the super-coating, producing therefrom a bituminous cement of higher penetration than the inner coating and serving as the binder which bonds together the individual particles of the aggregate to forma paved road surface which is tough, malleable, durable, wear-resisting and water-proof. V

In accordance with my invention, the quantities, as well as the consistencies of the two bitumens used for the inner coating and the super-coating may vary as to local needs of roadway conditions, traific, climate and available materials. An'old roadway foundationmay have ample supporting strength, but needs a thin'protecting wearing surface to prevent rapid wear and the entrance of water. Another old pavement may be so badly worn that its supporting strength must be supplemented or increased to meet heavier traflic. An entirely new pavement may be calledfor. In any of these events my new road-surfacing composition and the method of making the same provides a superior means for economically serving such roadway conditions. The followingexamples, taken from actual usage of-my invention, will serve to guide those skilled in the art in the application thereof.

will

A city pavement' of ample supporting strength, but so badly cracked that water thus admitted to the foundation was weakening the structure, could be preserved and The voidage in this sand indicated that for such use 8% of 6070 penetration asphalt would supply the desired bond and make the surface water-proof. I have found that 30 parts of a bituminous flux containing 70% of 100 penetration asphalt, amalgamated with 70 parts of 27 penetration asphalt produced an asphaltic cement having a penetration of 50, and that each percent of flux added raised that penetration three points. Therefore, to raise the penetration from the 50 named to the 65 required, would require the addition of 15/3 or of the flux, making the required total parts of flux 35 and of the hard asphalt 65. Therefore, in this case,

'the 8% by weight would be made up of 35 parts of a bituminous flux containing 70% of 100 penetration asphalt and65 parts of 27 penetration asphalt. That is to say, the

stable asphalt sand would first be coated with 5.2% by weight of 27 penetration asphalt and to this coated aggregate there would be applied a super-coating made up of 2 .8% by weight of bituminousflux containing 70% of 100 penetration asphalt. V

A cracked and disintegrated concrete pavement had sunken in places and raised in others until it had to be resurfaced. To level it up, ready for a wearing surface, required the use of an asphaltic binder course averaging 1 inches thick, composed of 1 inch crushed stone, which would need 5% by weight of 65 penetration asphalt as a cementing medium. Using the same method of calculation as outlined above gives 1.75% of fiuX and 3.25% of the hard asphalt, that is to say, the crushed stone would first be coated with 3.25% of 27 penetration asphalt to which a super-coating would be directly applied consisting of 1.75% by weight of a bituminous flux containing 70% of 100 penetration of asphalt. The half-inch wearing surface designed to be placed on this binder course, called for the use of aggregate passing the inchring and retained on a 10 mesh screen. Its voidage called for the use of 7.33% of asphalt and the traffic and climatic conditions allowed the use of an asphalt as soft as 95 penetration. Such calculations as to the amount and consistency of the binding media, being common to those skilled in the art, need not be discussed here. Thecalculation necessary to provide 7.33% by weight of 95 penetration asphalt, in ac- .cordance'with my invention, issimilar to that given above, that us, to raise the penenation from 50 to 95,.a. total of 45 points, calls for 45/3 orthe addition of-% more flux, making a total of parts of flux and parts of the heavy asphalt. 45% of the required 7.33% is approximately 3 A;% flux, leaving the remainder of the 7 or 4%, of the hard asphalt. In other words, in this instance, I would first coat the aggregate with 4% by weight of 27 penetration asphalt and then apply thereto a super-coating of 3 by weight of a bituminous flux containing of 100 penetration asphalt.

It will be apparent from the foregoing description that a road-surfacing composition in accordance with my invention is mobile and readily workable at ordinary atmospheric temperatures and that it does not require the application of extraneous heat thereto to render it workable. It is, therefore, a material which can be stored for considerable periods and transported for considerable distances from the place of manufacture to the place of use and still retain its mobility and workability. No eX- traneous heat is required to put this material in shape for distribution and leveling on the road-bed, and it is caused to set to form a paved surface by the application of pressure thereto. This pressure may be applied by a road roller or, in some cases, by the wheels of traffic. An important feature of the use of this road-surfacing composition is that a pavement can be constructed therefrom with but little interruption to traffic, inasmuch as traffic can be allowed to pass over the road as soon as the material is spread and set by the application of pressure, and this setting takes place almost immediately upon the passage of a road roller thereover. The foregoing specific examples will make it clear how the characteristics of the binder for the particles of aggregate in the finished roadway can be selected and controlled by choosing bituminous cement and bituminous flux of proper consistency for the inner coating and the super-coating, and using these in predetermined proportions. The composition has a distinct advantage over the usual hot mixes, in that it may be spread in thin or thick layers, as conditions may require, and the upper wearing surfaces may be laid with aggregates containing a very high percentage of bituminous material without reducing or impairing the workability of the composition as contradistinguished from the hot mixes which are limited in the percentage of bitumen employed, for, in the latter, usually from 10% to 11% of the bitumen is unworkable in thin layers on the road or street surface, due to the difiiculty of raking, or similar modes of leveling and distributing the mixture. My road-surfacing composition can readily be laid in strata under an inch thick without the checking and cracking that occurs in rolling such layers of the hot mixes. Also, it can be handled in layers over three inches thick, without waiting for partial cooling, as must be done with hot mixes.

It has been the common practice to mix the heavy bitumen with quick volatiles to produce cut-backs. The object is to render the heavy bitumen sufficiently fluid for working cold. The so-called quick volatiles have been manufactured at temperatures vastly greater than will be produced by the heat of the sun. Therefore, they will be slow to evaporate when subjected only to the heat of the sun. Also, when entrained between the molecules of the heavy bitumens, such evaporation becomes enceedingly slow. In fact, several cut-backs have beenfound to retain an appreciable per cent of the quick volatiles for some months after being spread upon the roadway surface. My mixture offers a very marked advantage over the use of cut-backs, because it is much less expensive, the quick volatiles costing moreand being wasted through evaporation, and because such quick volatiles as remain in the cut-back prevent it either regaining the consistency of the heavy asphalt or, in fact, regaining or retaining any stable consistency at all.

One advantage of the use of my improved road-surfacing composition is that the bituminous flux acts as a sort of priming coat for the foundation and thus a better bond is formed between the pavement formed by the use of my composition and the foundation. When this road-surfacing composition has been spread in layers on the foundation and pressure applied thereto, amalgamation of the bituminous flux and the inner coating of bituminous cement takes place, forming a binder which constitutes the bond between the individual particles of the aggregate. However, between the points of contact of coated particles there are areas where there is no compression. On these areas there is no instant amalgamation, because there is no external pressure. This provides a reserve supply of live unamalgamated bitumen for future use to serve when traffic has ultimately worn down the aggregate sufficiently to bring it under pressure and to call it into service.

With my composition, a paved surface is formed which is rough or file-like, and thus provides a better non-skid traction surface, but, notwithstanding this, the individual particles of the aggregate are so thoroughly bonded together by the bituminous cement formed by amalgamation of the two coatings that the road surface is thoroughly waterproof and water cannot penetrate it.

It will be apparent that, with my road-surfacing composition which retains its mobility and workability prior to the application of pressure, the material maybe distributed and leveled and evened to the desired surface contour in the cold, and this contour will be retained because the material is immediately set by the application of pressure, as when a road roller passes over it. The road-surfacing composition of my invention enables me to reduce the cost of of bituminous surfaces, regardless of the kind I and sizes of aggregates used. For instance, I may use any of the standard aggregate gradings, including sand, common to sheet asphalt, asphaltic concrete and the like, and the composition produced from such aggregate can be laid cold in thick or thin layers and have the same resultant commercial advantages after amalgamation as would be obtained with the aggregates of the size and kind herein mentioned by way of specific example. My invention is not to be confined, therefore to any particular grade or size of aggregate.

What I claim is:

1. The method of preparing a mobile and workable road-surfacing material, which can be laid cold and set to form a paved, wear tures, consisting of a mineral aggregate the individual particles of which have an inner coating of stable bituminous cement and an outer coating, applied directly to said inner coating, of a bituminous flux, devoid of light volatile matter, fluid at such atmospheric temperatures, and capable of amalgamation with said inner coating to form a bituminous cement of higher penetration than said inner coating.

In testimony whereof I aflix my signature.

SAM-E. FINLEY. 

